The innovation engine for new materials

Graham Sharp

Graham Sharp


CCS Physics


University of California, Santa Barbara


Sattvic Ray

Faculty Sponsor(s): 

Zvonimir Dogic

Faculty Sponsor's Department(s): 


Project Title: 

Using Embedded Forces to Take Quantitative Measurements of a Contractile Active Network

Project Description: 

Actin is a protein which plays a crucial role in the development and function of Eukaryotes, as it is both a major component of the cytoskeleton and of muscle filaments. By adding molecular motors such as myosin, we can weave actin filaments into an active contractile network, mimicking its biological function. Quantitatively measuring the stress and strain fields in actin networks is an important next step in understanding the physics of developmental biology, and in the creation of bioinspired materials. In order to calculate the stress and strain fields in the network, we propose a method of mechanically embedding externally controlled forces into the network. By binding paramagnetic beads to actin filaments and utilizing the dipole-dipole repulsion of the beads, we can create our own internal repulsive forces to compare to the active contractile forces. We have so far succeeded in robustly attaching beads to an actin network by coating them with gelsolin, an actin-binding protein. We have also demonstrated that geometrical confinement will work as intended by making a colloidal suspension of beads in water. When placed in an external field the beads repelled each other as expected and became uniformly dense locally. In the coming months we hope to embed these beads in an active network, and see an arrest of motion, indicating an active steady state solid. By making these measurements we can advance our quantitative understanding of biological and bioinspired tissues, and develop a new tool for measuring forces in active materials generally.